Stabilization



reamed Apr, 17, 1945 srsnruzarron Howard It. Peterson, Chicago, 111., H. Kaolin-en, Mnnsielflnd minors to Standw momma; Chicago, 11]., a corpora tion of No application m1. so, 194:, Serial-No. 4:11.10:

12 Claims. (Cl. 106-17) This invention relates to parafiin wax compositions. More particularly it relates to paraffin wax compositions having marked high temperature stability and to methods of producing such compositions.

Parafiln waxes or compositions comprising var-.- ious but generally high proportions of paraflin wax have found extensiveuse in coating and impregnating paper to be used for wrapping purposes, especially as food wrappers. when either the coating or impregnating technique is used,'

the paper is passed through a bath containing the molten paraflin wax composition to be applied. In general, it is inadvisable to allow the bath to attain a temperature in excess of about 180 F. to avoid oxidative deterioration of the wax. However, accurate controlof the bath temperature cannot always be achieved, with the result that loc l overheating sometimes brings parts of the bath to temperatures as high as 250 to 300 F. Furthermore, in the preparation of the so-cailed dry wax papers, which are papers whose fibers have been thoroughly impregnated with parafiin wax, the drying rolls must operate at a high temperature, usually in the range of 180 to 225 F., to drive the wax, whichhas been applied as a surface coating, into the fibers.

In addition it has been found essential to subject wax to a temperature of about 250 F. in order to pulp it with rubber-like materials to produce compositions suitable for paper, coating to produce food wrappers.

When wax or compositions comprising high proportions of paraffin wax are subjected to temperatures in excess of about 200 F., rapid oxidative deterioration of the wax sets in. This deterioration may be estimated by means of a test to be described hereinafter; it manifests itself to the consumer-by odor development, color formation, loss in sealing strength, and loss of other desirable properties.

In spite of the fact that parafiln wax reacts I slowly with atmospheric oxygen at temperatures high temperatures of the order of 200 I". or higher. especially at temperatures above about 250 F. .Another object of this invention is to provide inhibitors which will stabilize parafiin wax compositions against high-temperature atmospherie oxidation. A further object of this invention is to provide processes for securing high temperature stability in parafiin wax composition's.

We have discovered that crude petrolatum waxes of the type obtainable from Salt Creek crude oil may be treated to recover substances which function as inhibitorsto prevent oxidation 7 of parafiin wax compositions, particularly at high The high temperature inhibitors temperatures. present in crude petrolatum of the type obtain,- able from Salt Creek crude oil have been removed and lost by therefining processes used t9 transform the crude petrolatum into the refined white petrolatum of commerce. To prepare a crude petrolatum wax, a crude oil of the Salt Creek type may be reduced by distillation to about 40% bottoms, which is treated below about 180 F., atmospheric oxidation resulting in substantial loss of desirable wax properties proceeds rapidly at temperatures in excess of about 200 F. The problem encountered is aggravated by the fact that chemical stabilizers which are generally eflective in inhibiting low temperature atmospheric oxidation of parafiln wax are generally ineffective at high temperatures 0 about 200 F. and higher.

It is an object of this invention to provide paramnwax compositions which are stable for long with concentrated sulfuric acid to remove various impurities, such as nitrogen and sulfur compounds, unsaturated materials and the like. The

acid treated bottoms are neutralized and, op-' tionally after further reduction by distillation. diluted with naphtha. The naphtha solution is centrifuged to produce a very crude petrolatum yellow micro-crystalline w'ax having an oil content-less than about10%, and usually in,the range of about'2to about 5%. The melting point of the crude petrolatum wax, may vary from about to about F. I I

Ordinarily crude petrolatum wax is converted to the salable refined state by refining with clays or other adsorbentsand/or by extraction with solvents which remove most of the oil, coloring matter and other impurities.

We have found that the addition of about 0.5 to 10% of. a. Salt Creek type crude petrolatum to a refined paraflln wax exerts a very considerable inhibiting action upon the latter to prevent/oxidative deterioration at temperatures in the neighborhood of 200 F. and higher, where ordinary chemical antioxidants for wax fail to function eifectively. Crude petrolatum wax of the type obtainable from Salt'Creek crude oil contains small amounts of unidentified substances which function as oxidation inhibitors particularly at periods of time against a oxidation at 65 high temperatures, when addedto parafiin wax compositions. The Salt Creek type of petroiatum is quite unique in.that relatively small proportions thereoi, e. g., less than about 10%, confer high temperature oxidation stability up n compositions comprising substantial proportions of parafiln wax without deleteriously aifecting other desirableproperties of the refined'parafiln wax, such as tensile strength, sealing strength and A desirable blocking and scumng characteristics.

- or otherwise contacted with an adsorbent such as an acid-treatedmontmorillonite clay, active carbon, silica gel, alumina or the like, either alone or in the presence of a diluent. A suitable diluent is a relatively narrow boiling range paramnic naphtha, e. g., a virgin c naphtha boiling in the range of 200400 F. such as may be fractionated from Salt Creek crude oil. It should be understood that we may use any diluent which will serve practically to dilute the petrolatum and to reduce its viscosity. During the filtration or contacting of the crude petrolatum, the inhibitor is selectively adsorbed by the adsorbent material and may be recovered therefrom by washing with suitable solvents. Suitable solvents for the recovery of the adsorbed inhibitor include B,B' lichlorodiethylether (Chlorex) furfural. nitromethane, nitrobenzene, phenol, benzol, alcohols, ketones, ethers, chlorinatedaliphatic hydrocarbonssuch as methyl chloride, ethylene dichloride, trichloroethylene, and the like, used separately, successively or in mixtures. We may use the solvent mixtures shown in U. S. Patent 1,805,178. The solvent extract may be treated, e. g., by freetional distillation. to recover solvent for reuse in the process and aconcentrate of the inhibitor.

Another method of preparing a concentrate of the inhibitor comprises extracting the crude petrolatum with a selective solvent. We may operate at a temperature sufficient to effect substantial dissolution of the petrolatum, then allow the mass to cool if necessary to effect a separation into rafiinate and extract phases which may be separated from each other by known means, such as decantation, centrifuging or filtering. The inhibitor is concentrated in the extract phase. The solvent and the inhibitor dissolved in the extract phase may then be separated, as by distillation, to yield recycle solvent for the extraction process and an inhibitor concentrate. Suitable selective solvents for this process include those which have been mentioned above for the recovery of adsorbed inhibitor from the adsorbent.

The inhibitor may likewise be concentrated by centrifuging a crude petrolatum of the Salt Creek type in a parafilnic naphtha solution. Efiiuent oil from the centrifuge is stripped of gasoline boiling range hydrocarbons to produce a Centrifuge Oil in which the inhibitor is present in much higher concentrationthan in the petrolatum from which it was derived. 1 The concentrate ofthe inhibitor may be obtained from a crude petrolatum of the Salt Creektypebyfractionation with aliquefiednormally gaseous hydrocarbon or hydrocarbon mixture, e. g., a refinery propane fraction. An inhibitor concentrate may be obtained by leaching the petrolatum with the liquefied normally gaseous hydrocarbon at relatively low temperatures, e. g.. about 0 to about 50 F. with refinery propane, filtering the wax from the solution of inhibitor in the liquefied normally gaseous hydrocarbon and thereafter evaporating the latter to leave the desired concentrate as a residue. Alternaflvely, the inhibitor concentrate may be produced by fractional precipitation from a liquefied normally gaseous hydrocarbon, suitably refinery propane, under conditions approximating the critical temperature and pressure of the precipitation medium.

Although certain specific methods of obtaining inhibitor concentrates have been described these should not be considered limitative, but merely illustrative. ;Alternative and equivalent methods will readily suggest themselves to one an inert atmosphere (nitrogen or carbon dioxide) with a solution of ferrous thiocyanate'for a short period and then allowed to settle. The color of the aqueous phase is then compared with the color obtaiped by adding ammonium thiocyanate to diluted samples of standard ferric chloride. Choosing the solution which gives the same color depth as the test sample (interpolating if necessary) the parts per million of iron in the solution is called the peroxide number of the oil.

The following Indiana Peroxide Test data is adduced'to show the effects of specific applications of our invention. All percentages are by weight. In the tests, wax B is a refined Daraflln wax melting at -l37 F. T. B. C. is an abbreviation for tertiary butyl catechol which is known to be a low temperature oxidation inhibitor for wax. Similar results are ob-' tainable by the use of other low temperature oxidation inhibitors. The crude Salt Creek pet- 'rolatum was prepared in accordance with the method previously described herein. The Extract Filter Oil was prepared by filtering the crude Salt Creek petrolatum through a bed of clay and washing the used clay with hot naphtha. Wax C is a refined paraffin wax melting at 122- 124" F. The Centrifuge Oil was prepared by centrifuging a naphtha solution of an oil-bearing crude Salt Creek petrolatum at a temperature below the wax solution/temperature therein, and

the naphtha from the eilluent oil.

In considering the significance of the peroxide nunmers obtained by the use of the Indiana Peroxide Test, it haslbeen found that peroxide numhers above about 8-10 at the end of about 10 hours indicate that the parafiln wax composition is no longer salable because of odor and color development and loss of sealing and tensile strength and the loss of other desirable properties. Peroxide numbers not exceeding about 8-10 at the end of 10. hours indicate that the paramn wax composition may be satisfactorihr applied as a coating and impregnating medium.

Table I v Peroxide numbers sitar indicated hours oi heating Wax composition Wax "B" 300+ WaxB+3% crude 'Salt Creek petrolatum W a x B+0.057

Extract Filter oil.

W lExwpetrolatum From the above test data it will be noted that refined paraffin waxes, alone or compounded with a normal proportion of a low-temperature oxidation inhibitor such as tertiary butyl catechol, rapidly deteriorate to a point where they can no longer be used satisfactorily as coating or impregnating agents. The addition of 3%' of a crude Salt Creek petrolatum aids considerably in increasing the wax stability but much greater increases in wax stability result from the addition of an inhibitor concentrate such as Centrifuge Oil or Extract Filter Oil.

In general, we have found that about 0.05 to about 3% of our inhibitor concentrates may be added to paraflln waxes to secure satisfactory high temperature stability. However, somewhat higher or lower proportions of inhibitor concentrate may be used, depending on the character of the paraffin wax composition, the contemplated conditions for use of the paraflin wax composition, the nature of the specific inhibitor concentrate and the degree of stability to oxidative deterioration which it is desired to impart.

It is apparent that we havediscovered paraflln wax compositions characterized by their oxidative stability at high temperatures, and processes for making same. We have also discovered high temperature oxidation inhibitors for paraffin wax compositions and methods for their production.

We claim:

l. A composition of matter comprising a paraffin wax and an oxidation inhibitor separated as an impurity from a crude petrolatum, said oxidation inhibitor being ineffective substantially to increase the tensile strength or the said paraffin wax.

2. A composition of matter comprising a paraffin wax normally subject to oxidative deterioration at temperatures above about 200 F. and an inhibitor for said oxidative deterioration derived from a crude petrolatum and substantially free of refined petrolatum, the tensile strength of the a said paramn wax not being substantially increased by the presence of the said oxidation in-. hibitor.

3. A composition of matter comprising a. parafiin wax normally subiect to oxidative deteriora 70 tion at temperatures above about 200 F. and an inhibitor for said oxidative deterioration separated as an impurity from a crude petrolatum, said inhibitor being present in a small but sufficient proportion to inhibit said oxidative deterioration without increasing substantially the tensile strength of the said paraffin wax.

4. A composition of matter comprising a paraffin wax and an oxidation inhibitor separated as an impurity from .a crude petrolatum of the type obtainable from Salt Creek crude oil said oxidation inhibitor being inefiective substantially to increase the tensile strength of the said paraflln wax.

5. A composition of matter comprising a paraffin wax and about 0.05 to about 3% of an oxidation inhibitor concentrate prepared from a crude petrolatum of the type obtainable from Salt Creek crude oil, the tensile strength of the said paraffln wax not being substantially increased by the presence of the said oxidation inhibitor.

6 A composition of matter comprising a paratfin wax and an oxidation inhibitor prepared from a crude petrolatum of the type obtainable from Salt Creek crude oil by treatment with an adsorbent material followed by extraction of the said adsorbent material with a solvent to segregate said oxidation inhibitor, said oxidation inhibitor being ineffective substantially to increase the tensile strength of the said paraffin wax.

7. A process for stabilizing a composition of matter comprising a substantial proportion of a parafiin wax, comprising adding to said composition of matter between about 0.3% and about 5.0% of a crude petrolatum of the type obtainable from Salt Creek crude oil. I

8. A composition of matter comprising a, paraffln wax and an oxidation inhibitor derived from a crude petrolatum of the type obtainable from Salt Creek crude oil by centrifugal fractionation, said oxidation inhibitor being substantially free of refined petrolatum and inefiective substantially to increase the tensile strength of the said paraffin wax.

9. A composition of matter comprising a paraffln wax and an oxidation inhibitor separated as an impurity from a crude petrolatum of the type obtainable from Salt Creek crude oil by fractionation with a normally gaseous liquefied hydrocarbon, said oxidation inhibitor being ineflective substantially to increase the tensile strength of the said paraflin wax.

10. A process of stabilizing a composition of matter comprising a substantial proportion of a paraflln wax, comprising incorporating in said composition of matter an oxidation inhibitor de rived from a crude petrolatum.

11. The process of claim 10 where the crude petrolatum is of the type obtainable from Salt Creek crude oil.

12. A process of stabilizing a composition of matter comprising a substantial proportion of a paramn wax, comprising adding to said composition or matter between about 0.05 and about 3% of an oxidation inhibitor derived from a crude petrolatum of the type obtainable from Salt Creek crude oil.

HOWARD R. PETERSON. FREDERICK H. MACLAREN. 

